Method of using sulfonate blends for improved oil recovery

ABSTRACT

Improved oil recovery is realized by flooding oil-bearing subterranean formations with an aqueous mixture, preferably a micellar dispersion, comprised of at least two different petroleum sulfonates, the sulfonates have an average equivalent weight within the range of about 390-450, and have an aliphatic to aromatic proton (A/AP) ratio within the range of 4-20 moles per mole but the two sulfonates have a difference in their respective A/AP ratio of at least 2.5 moles per mole.

[11] 3,901,317 Aug. 236, 1975 1 1 METHOD OF USING SULFONATE BLENDS FOR IMPROVED OIL RECOVERY [75] Inventors: Mark A. Plummer; Wayne 0.

Roszelle, both of Littleton, C010.

[73] Assignee: Marathon Oil Company, Findlay,

Ohio

22 Filed: Aug. 10, 1973 21 Appl. No.: 387,413

[52] US. Cl. 166/274; 166/273; 252/855 D [51] Int. Cl. EZlB 43/22 [58] Field of Search 166/273-275, 166/305 R, 252; 252/855 D [56] References Cited UNITED STATES PATENTS 3.096820 7/1963 Bernard 166/274 3,288.213 11/1966 King et a1.

3.434.542 3/1969 Dotson 3,500,912 3/1970 Davis, Jr. et a1. 166/252 3,506,070 4/1970 Jones 166/273 3,508,612 4/1970 Reisbcrg et a1. 166/275 X 3,623,553 11/1971 Burdge 166/274 X 3,638,728 2/1972 Hill 166/273 3,653,437 4/1972 Gale ct a1 166/275 X 3,776,309 12/1973 Murray ct a1. 166/274 X Primary Examiner--Stephen J. Novosad Attorney, Agent, or Firm.1oseph C. Herring; Richard C, Willson, Jr.; Jack L. Hummel 5 7 ABSTRACT Improved oil recovery is realized by flooding oilbearing subterranean formations with an aqueous mixture, preferably a micellar dispersion, comprised of at least two different petroleum sulfonates, the sulfonates have an average equivalent weight within the range of about 390-450, and have an aliphatic to aromatic proton (A/AP) ratio within the range of 420 moles per mole but the two sulfonates have a difference in their respective A/AP ratio of at least 2.5 moles per mole.

22 Claims, N0 Drawings emoir or usiNe SULFONATE BLENDS FOR i PRovEn on. RECOVERY BACKGROUND 'OF'THE INVENTION 1.. Fieldof the lnvention An aqueous mixture of petroleum sulfonates is in jected into a subterranean formation and displaced toward a production means to recover crude oil therethrough Description of the Prior Art Aqueous petroleum sulfonate mixtures are effective to recove r crude oil in primary, secondary, and tertiary recovery processes. For example, the mixture can be injected into an oil-bearing subterranean formation and displaced towards a production well to recover crude oil. Mobility buffer slugs, i.e. aqueous solutions containing mobility reducing agents, can be injected behind the mixture to improve oil recovery.

.U .S. Pat. Nos. 3,254,714 and 3,275,075 to Gogarty at A1; 3,497,006 to Jones et al. and 3,506,070 to Jones teach processes using petroleum sulfonate in micellar dispersions.

The prior art teaches that the petroleum sulfonates desirably have an average equivalent weight within the range of 350 to 525. Other additives may be present in the aqueous petroleum sulfonate mixture to enhance oil recovery, e.g. hydrocarbon, cosurfactant, electrolyte, mobilityreducing agent, viscosity reducing agent,

etc.

.Applicants have discovered a novel combination of petrole urn-sulfonates to obtain a more efficient oil recovery process.

' 'SUMMARY or THE INVENTION Applicants recover increased amounts of oil using as aqueous petroleum sulfonate mixture containing at least two different petroleum sulfonates, the sulfonates have an average equivalent weight within the range of about 390-450 and preferably 395440, the hydrocarbon portion of the sulfonate has an average aliphatic to aromatic proton (A/AP) ratio within the range of about 4-20 moles per mole (i.e. the average sulfonate molecule contains 4-20 aliphatic protons per aromatic proton) but the different sulfonates have a distribution or difference in their respective A/AP ratio of at least 2.5 moles "per mole. Optionally, a viscosity increasing agenfia mobility reducing agent, corrosion inhibitors, oxygen scavengers, cosurfactant, electrolyte, etc, or combinations of two or more of these materials can be incorporated into the aqueous sulfonate mixture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aqueous petroleum sulfonate mixture contains at least two different petroleum sulfonates, i.e. the hydro to about 1 percent or more by weight of the viscosityincreasing agent and/or mobility reducing agent and the residue aqueous medium (preferably at 5 to about percent byvolume). The aqueous mixture can be a micellar dispersion (this term as used herein includes micellar solution and microemulsion), an emulsion, so lution, etc. I l

The aqueous medium can be soft water, water containing minor amounts of salts, or brackish water. The cosurfactant can be an amine, aldehyde, ketone, hydroxy-containing compound (including conventional alcohols), ester, ether, or similar compound containing one or more of hydroxy, oxy, amide, halide, etc; the cosurfactant contains 1 to about 20 or more carbon atoms and preferably about 3 to about 8 carbon atoms. Numerous electrolytes are useful; preferably they are inorganic acids, inorganic bases, and inorganic salts. The hydrocarbon can be crude oil, a partially refined fraction of crude oil, or refined fraction of crude oil, or synthetic hydrocarbon (including halogenated hydrocarbons); the hydrocarbon can be unreacted hydrocarbon within the petroleum sulfonate. Examples of patents which teach particular components useful in the aque ous sulfonate mixture include: U.S. Pat. Nos. 3,254,714 to Gogarty et al; 3,307,628 to Sena; 3,330,343 to Tosch et al; 3,356,138 to Davis et al; 3,297,084 to Gogarty et al; 3,476,184 to Davis; 3,497,006 to Jones et a1; 3,493,047 to Davis et a1; 3,493,048 to Jones; 3,500,912 to Davis et a1; 3,504,744 to Davis et a1; 3,506,070 and 3,506,071 to Jones; and 3,508,611 to Davis et al.

Examples of viscosity increasing agents are the biopolymers such as polysaccharide polymers (e.g. defined in U.S. Pat Nos. 3,020,206 to Patton et a1 and 3,020,207 to Patton) or any high molecular weight organic polymer that tends to increase the viscosity of the water and which will not substantially sorb onto the reservior rock. Examples of mobility reducing agents include acrylamide polymers, e.g. the partially hydrolyzed, high molecular weight polyacrylamides such as the Pusher polymers marketed by Dow Chemical Co., Midland, Mich; copolymers of acrylamide and acrylic acid or sodium acrylate, Nsulfohydrocarbonsubstituted acrylamides (e.g. defined in U.S. Pat. No 3,679,000 to Kaufman), and commercially available polymers such as Betz Hi-Vis and Betz-Uni-Perm polymers (Betz Laboratories, Inc., Trevose, Pa.), acrylamide polymers sold by Calgon Corporation, Pittsburgh, Pa., and acrylamide copolymers marketed by Nalco Chemical Co., Chicago, 111. Any high molecular weight polymer which tends to reduce the mobility of the aqueous surfactant mixture flowing through the reservoir rock is useful with this invention. The agents can 0.05 percent and more preferably about 0.02 to about 0.1 percent by weight, based on the aqueous mixture. Other additives, such as corrosion inhibitors, oxygen scavengers, bactericides, etc. can be added to the mixture.

' The petroleum sulfonates can be obtained by sulfonating hydrocarbon feedstocks, e.g. heavy vacuum gas oil, having molecular weights within the range of about 300 to about 650 and more preferably about 400 to about 470. Sulfonation of the feedstock is effected by methods known in the art, eg with oleum or sulfur trioxide in the absence or presence of a solvent such as ethylene dichloride, sulfur dioxide, unreacted hydro carbon, etc. The sulfonic acid is neutralized with a basic compound such as sodium hydroxide, ammonia, ammonium hydroxide, etc.

As mentioned previously, at least two different petroleum sulfonates are used. These petroleum sulfonates have an average equivalent weight within the range of about 390 to about 450 and preferably about 395 to about 440. The petroleum sulfonates have an average A/AP ratio within the range of about 4 to about 20 moles per mole and more preferably about 9 to about moles per mole -that is 4 to aliphatic hydrogen protons per aromatic hydrogen proton are present in the hydrocarbon portion of the petroleum sulfonate. However, the A/AP ratios of the at least two petroleum sulfonates must have a distribution or difference of at least 2.5, i.e., the average A/AP ratio of one sulfonate must be different from the average A/ AP ratio of the other sulfonate by a magnitude of at least 2.5 and preferably at least 3 and more preferably at least 3.8.

To obtain the two different petroleum sulfonates, at least two different feedstocks are generally preferred. One feedstock can have, for example, an average molecular weight range of about 400-430 while the other one can have an average molecular weight range of about 430-470. Also, the feedstocks should be of sufficient hydrocarbon character to obtain the desired A/AP ratios as indicated above.

Examples of volume amounts of useful aqueous petroleum sulfonate mixtures injected into the reservoir are about 1 to about 50 percent or more formation pore volume, preferably about 1 to about 15 and most preferably about 2 to about 10 percent formation pore volume. Larger pore volumes are, of course, useful where the economics of the process justifies same.

Preferably, the aqueous sulfonate mixture is followed by a mobility buffer slug. The mobility buffer slug is preferably an aqueous solution containing a mobility reducing agent such as a partially hydrolyzed, high molecular weight polyacrylamide, e.g. the Pusher polymers marketed by Dow Chemical Co., Midland, Mich, a high molecular weight polyalkylene oxide polymer, high molecular weight acrylamide polymers containing sulfo grouping (e.g. those defined in US. Pat. No. 3,679,000 to Kaufman), acrylamide copolymers (e.g. copolymers of acrylamide and sodium acrylate), etc., biopolymers (preferred in low permeability reservoirs) and any high molecular weight polymer that is compatible within the reservoir and which tends to reduce the mobility of the aqueous solution flowing through the reservoir rock. The mobility buffer can be injected into the reservoir in volume amounts of about 5 to about 150 percent, preferably to about 75 percent and more preferably 50 to about 60 percent formation pore volume. The mobility reducing agent can be present in concentrations of about 50 to about 2,000, preferably about 100 to about 1,500 and more preferably about 200 to about 1,000 ppm, based on the water.

A water drive is injected into the reservoir to displace the aqueous sulfonate mixture and optionally the mobility buffer toward a production well to recover crude oil therethrough. Preferably, the water is compatible with the back portion of the mobility buffer and/or the aqueous sulfonate mixture, e.g. preferably it does not substantially leach water soluble components out of the preceding slug. Where the water drive contains ions, it is preferred that these ions are compatible with those within the reservoir.

Preferably, the mobility profile of the overall process is graded from a low mobility equal to or less than the mobility of the combination of formation fluids (crude oil and interstitial water within the formation) to a high mobility equal to or approaching that of the injected water drive. The mobility of the front, mid-section, and back portion of the mobility. buffer and optionally of the aqueous sulfonate slug can be designed by adjusting the viscosity and/or mobility agent concentration to obtain desired mobility characteristics to the process.

EXAMPLES Examples are presented to teach specific embodi ments of the invention. Unless otherwise specified, all percents are based on volume:

Petroleum sulfonates are obtained by sulfonating different heavy vacuum gas oil feedstocks. For example, sulfonates A and B are obtained from feedstocks having average molecular weights of 400-430 and 430-470, respectively. Sulfonation is effected with sulfur trioxide in the presence of a diluent and the sulfonic acids are neutralized with ammonia. The resulting average equivalent weights of petroleum sulfonates A and B are 401 and 423 and have A/AP ratios of 9.6 and 13.4, respectively. Sulfonates C-D are obtained by same process except the feedstocks and process conditions are changed to give sulfonate properties indicated in the following examples. Micellar dispersions are prepared with these petroleum sulfonates by blending the following components:

Weight Percent petroleum sulfonate a) SO NH portion of the The micellar dispersions are used to flood core samples in Example 1.

EXAMPLE I Berea sandstone core samples 4 feet long and 3 inches in diameter are first saturated with water, then flooded with oil and thereafter flooded with water to residual oil saturation. Thereafter, 2 percent formation pore volume of the micellar dispersion, containing petroleum sulfonates having properties exhibited in Table 1, are injected into the core samples. The micellar dispersion is followed by at least one formation pore volume of water containing 1,000 ppm of Pusher 700 polymer (a partially hydrolyzed, high molecular weight polyacrylamide marketed by Dow Chemical Co., Midland, Mich). The results of the core flooding, the sulfonate properties and the properties of the micellar dispersion are indicated in Table 1:

TABLE I HIGH OIL-RECOVERY EFFICIENCIES OBTAINED WITH SULFONATE BLENDS EXHIBITING APPROPRIATE EQUIVALENT WEIGHT AND A/AP AVERAGES AND DISTRIBUTIONS Sulfonate Properties Properties of Mieellar Dispersions Blend Ratio Eq. Wtv Average A/AP Avg. Viscosity at 72F. Electrolyte Oil-Rec. Wt 'WIYI Distrib. Eq. Wt. Distrih. A/AP Centipois'es Content-Wt: Efficiency Run No. Ratio (NH ,SO CaCl Vol.

I 50-A/50-B 401-423 412 9.6l3.4 I 1.5 62 0,50 0.00 32.6 2 25-C/75-D 400-426 419 9.6l3.4 12.5 28 0.50 0.00 78.0

EXAMPLE II EXAMPLE IV This example is presented to show oil recoveries with A 4 feet long by 3 inches diameter Berea sandstone similar sulfonates in micellar solutions. The flooding core in a tertiary condition is flooded with 5 percent procedure defined in Example I is followed; results of pore volume of an aqueous mixture containing 8 perthe tests are presented in Table 2: cent of a 50-50 mixture of sulfonates C and D. 200

TABLE I1 POOR OIL-RECOVERY EFFICIENCIES OBTAINED WITH SULFONATE BLENDS EXHIBITING INAPPROPRIATE EQUIVALENT WEIGHTS Blend Ratio Eq. Wt. Average A/AP Avg. Viscosity at 72F Electrolyte Oil-Ree. Run No. Wt'7(/Wl 7( Distrib. Eq. Wt. Distrih. A/AP Centipoises Content-Wt.7r Effici- Ratio (NH.,) SO CaCl ency Vol.

3 50-E/50-F 362-460 405 96-114 I 1.5 49 0.50 0.00 64.8 4 60-G/40-H 417-451 430 96-134 11.1 48 0.50 0.00 66.6 5 40-I/60-J 393-428 413 9.6-134 11.9 0.42 0.03 70.1 6 50-K/50-L 380-423 400 9.613.4 1 1.5 42 0.50 0.00 75.6

Properties of Sulfonates:

sulfonate Average Equivalent Weight A/AP Ratio E 362 9.6 F 460 13.4 G 417 9.6 H 451 13.4 I 393 9.6 J 428 13.4 K 380 9.6 L 423 13.4

The petroleum sulfonates used in Table 2 do not have ppm of Pusher polymer 700 Series (a partially hydrothe appropriate equivalent weights, and thus lower oil lyzed, high molecular weight polyacrylamide marketed recoveries are obtained. by Dow Chemical Co.,). This aqueous sulfonate mix- EXAMPLE I] ture is followed by 50 percent pore volume of an aque- Also, poor oil recoveries are obtained with sulfonate ous slug containing 700 ppm of the Dow Pusher Polyblends exhibiting inappropriate A/AP ratio distribumer 700 Series. Thereafter, water is injected to distion. The cores are flooded as described in Example 1 45 place the two previously injected slugs through the and results are reported in Table 3: core. Substantial amounts of oil are recovered.

TABLE III POOR OIL-RECOVERY EFFICIENCIES OBTAINED WITH SULFONATE BLENDS EXHIBITING INAPPROPRIATE A/AP DISTRIBUTIONS Sulfonate Properties Properties of Mieellar Dispersions Ave. Difference Viscosity Electrolyte OilRec. Run Blend Ratio Eq. Wt. Average A/AP A/AP of A/AP at 72F Content-WL'fi Effici- No. WWI/WWI Distrib. Eq. Wt. Distrib. Ratio Ratio Centipoises (NH J SO CaCl ency Vol/71 7 X0-M/20-N 424-428 425 11.2-13.4 11.6 2.2 29 0.33 0.05 69.4 X -O/50-P 424-428 426 11.2-13.4 12.3 2.2 29 0.32 0.03 73.7

Properties of Sulfonates:

Sulfonate Average Equivalent Weight A/AP Ratio M 424 I 1.2 N 428 13.4 O 424 I 1.2 P 428 13.4

Table 3 indicates that without the appropriate A/AP EXAMPLE V distribution, less oil is recovered as compared to the pe- (,5 The process of Example IV is duplicated except the troleum sulfonates defined in Table 1 wherein the Pusher polymer within the aqueous sulfonate mixture A/AP distribution is at least greater than 2.5. slug is replaced with an equal amount Of K ll' midentified as a polysaccharide manufactured by Xanco Division of Kelco Corporation. Substantial amounts of oil are recovered by this process.

it is not intended that the above invention be limited by the examples. Rather, all equivalents obvious to those skilled in the art are intended to be incorporated within the scope of the invention as defined in the specification and appended claims.

What is claimed is:

1. An improved process of flooding an oil-bearing subterranean formation with an aqueous petroleum sulfonate mixture wherein the mixture is injected into the formation and displaced toward at least one production means in fluid communication with the reservoir to recover crude oil through the production means, the improvement comprising incorporating into the aqueous mixture at least two different petroleum sulfonates, the sulfonates defined as:

1. having an average equivalent weight within the range of about 390 to about 450,

2. having an aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moles/ mole, but

3. the sulfonates having different aliphatic to aromatic proton ratios of a magnitude of at least 2.5 moles/mole.

2. The process of claim 1 wherein the average equivalent weight of the petroleum sulfonate is within the range of about 395 to about 440.

3. The process of claim 1 wherein the aqueous sulfonate slug contains about 1 to about 20 percent by volume of the petroleum sulfonates.

4. The process of claim 1 wherein the petroleum sulfonates have an aliphatic to aromatic proton ratio within the range of about 9 to about moles/mole.

5. The process of claim ll wherein the distribution of the aliphatic to aromatic proton ratio of the two different petroleum sulfonates is of a magnitude of at least 3.0 moles/mole.

6. The process of claim 1 wherein the distribution of the aliphatic to aromatic proton ratio of the two different petroleum sulfonates is of a magnitude of at least 3.8 moles/mole.

7. The process of claim 1 wherein the aqueous sulfonate mixture contains one or more of hydrocarbon, cosurfactant, and electrolyte.

8. The process of claim 1 wherein the aqueous sulfonate mixture contains a viscosity increasing agent, a mobility reducing agent, or a combination of the two.

9. The process of claim 1 wherein the aqueous sulfonate mixture slug is followed by a mobility buffer slug.

10. The process of claim 1 wherein the mixture is a micellar dispersion.

11. The process of claim 1 wherein the mixture is an emulsion.

12. The process of claim 1 wherein the mixture is a micellar dispersion comprised of about 1 to about 90 percent hydrocarbon, about 5 to about 95 percent aqueous medium, about 0.0l to about percent of an amine, aldehyde, ketone, hydroxy-containing compound, ester, or ether containing l to about 20 carbon atoms. and about 0.001 to about 5 percent, based to the aqueous medium, of an inorganic acid. inorganic base or inorganic salt.

13. An improved process of flooding an oil-bearing subterranean formation wherein a micellar dispersion is injected into the formation and displaced toward at least one production means to recover crude oil therethrough, the improved process comprising using as a surfactant within the micellar dispersion a mixture of at least two different petroleum sulfonates defined as:

1. having an average equivalent weight within the range of about 390 to about 450,

2. having an average aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moles/mole, but

3. the sulfonates having different aliphatic to aromatic proton ratios of a magnitude of at least about,

2.5 moles/mole, and thereafter injecting the dispersion into the reservoir and displacing it toward the production means. v

14. The process of claim 13 wherein the average equivalent weight of the petroleum sulfonates is within the range of about 395 to about 440.

15. The process of claim 13 wherein the aliphatic to aromatic proton ratio of the petroleum sulfonates is within the range of about 9 to about l5 moles/mole.

16. The process of claim 13 wherein a mobility buffer slug is injected behind the dispersion.

17. The process of claim 13 wherein about 1 to about 50 percent formation pore volume of the micellar dispersion is injected into the reservoir.

18. The process of claim 13 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.0 moles/mole.

19. The process of claim 13 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.8 moles/mole.

20. An improved process of flooding an oil-bearing subterranean formation wherein a micellar dispersion comprised of hydrocarbon, petroleum and aqueous medium is injected into the formation and displaced toward at least one production means in fluid communication with the reservoir to recover crude oil through the production means, the improved process comprising injecting into the formation a micellar dispersion comprised of at least two different petroleum sulfonates, the sulfonates defined as:

1. having an average equilvalent weight within the range of about 395 to about 440,

2. having a aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moles/mole, but,

3. the sulfonates having different aliphatic to aromatic ratios of a magnitude of at least 3 moles/- mole.

21. The process of claim 20 wherein the petroleum sulfonates have an aliphatic to aromatic proton ratio within the range of about 9.4 to about 14.5 moles/mole.

22. The process of claim 20 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.8 moles/mole. 

1. HAVING AN AVERAGE EQUIVALENT WEIGHT WITHIN THE RANGEOF ABOUT 390 TO ABOUT 450,
 1. AN IMPROVED PROCESS OF FLOODING AN OIL-BEARING SUBSTERRANEAN FORMATION WITH AN AQUEOUS PETROLEUM SULFONATE MIXTURE WHEREIN THEMIXTURE IS INJECTED INTO THE FORMATION AND DISPLACED TOWARD AT LEAST ONE PRODUCTION MEANS IN FLUID COMMUNICATION WITH THE RESEVIOR TO RECOVER CUDE OIL THROUGH THE PRODUCTION MEANS, THE IMPROVEMENT COMPRISING INCORPORATING INTO THE AQUEOUS MIXTURE AT LEAST TWO DIFFERENT PETROLEUM SULFONATES THE SULFONATES DEFNED AS,
 2. having an aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moles/ mole, but
 2. HAVING AN ALIPHATIC TO AROMATIC PROTON RATIO WITHIN THE RANGE OF ABOUT 4.0 TO ABOUT 20 MOLES/MOLE, BUT
 2. The process of claim 1 wherein the average equivalent weight of the petroleum sulfonate is within the range of about 395 to about
 440. 2. having a aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moles/mole, but,
 2. having an average aliphatic to aromatic proton ratio within the range of about 4.0 to about 20 moLes/mole, but
 3. the sulfonates having different aliphatic to aromatic proton ratios of a magnitude of at least about 2.5 moles/mole, and thereafter injecting the dispersion into the reservoir and displacing it toward the production means.
 3. the sulfonates having different aliphatic to aromatic ratios of a magnitude of at least 3 moles/mole.
 3. the sulfonates having different aliphatic to aromatic proton ratios of a magnitude of at least 2.5 moles/mole.
 3. The process of claim 1 wherein the aqueous sulfonate slug contains about 1 to about 20 percent by volume of the petroleum sulfonates.
 3. THE SULFONATES HAVING DIFFERENT ALIPHATIC TO AROMATIC PROTON RATIOS OF A MAGNITUDE OF AT LEAST 2.5 MOLES/MOLE.
 4. The process of claim 1 wherein the petroleum sulfonates have an aliphatic to aromatic proton ratio within the range of about 9 to about 15 moles/mole.
 5. The process of claim 1 wherein the distribution of the aliphatic to aromatic proton ratio of the two different petroleum sulfonates is of a magnitude of at least 3.0 moles/mole.
 6. The process of claim 1 wherein the distribution of the aliphatic to aromatic proton ratio of the two different petroleum sulfonates is of a magnitude of at least 3.8 moles/mole.
 7. The process of claim 1 wherein the aqueous sulfonate mixture contains one or more of hydrocarbon, cosurfactant, and electrolyte.
 8. The process of claim 1 wherein the aqueous sulfonate mixture contains a viscosity increasing agent, a mobility reducing agent, or a combination of the two.
 9. The process of claim 1 wherein the aqueous sulfonate mixture slug is followed by a mobility buffer slug.
 10. The process of claim 1 wherein the mixture is a micellar dispersion.
 11. The process of claim 1 wherein the mixture is an emulsion.
 12. The process of claim 1 wherein the mixture is a micellar dispersion comprised of about 1 to about 90 percent hydrocarbon, about 5 to about 95 percent aqueous medium, about 0.01 to about 20 percent of an amine, aldehyde, ketone, hydroxy-containing compound, ester, or ether containing 1 to about 20 carbon atoms, and about 0.001 to about 5 percent, based to the aqueous medium, of an inorganic acid, inorganic base or inorganic salt.
 13. An improved process of flooding an oil-bearing subterranean formation wherein a micellar dispersion is injected into the formation and displaced toward at least one production means to recover crude oil therethrough, the improved process comprising using as a surfactant within the micellar dispersion a mixture of at least two different petroleum sulfonates defined as:
 14. The process of claim 13 wherein the average equivalent weight of the petroleum sulfonates is within the range of about 395 to about
 440. 15. The process of claim 13 wherein the aliphatic to aromatic proton ratio of the petroleum sulfonates is within the range of about 9 to about 15 moles/mole.
 16. The process of claim 13 wherein a mobility buffer slug is injected behind the dispersion.
 17. The process of claim 13 wherein about 1 to about 50 percent formation pore volume of the micellar dispersion is injected into the reservoir.
 18. The process of claim 13 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.0 moles/mole.
 19. The process of claim 13 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.8 moles/mole.
 20. An improved process of flooding an oil-bearing subterranean formation wherein a micellar dispersion comprised of hydrocarbon, petroleum and aqueous medium is injected into the formation and displaced toward at least one production means in fluid communication with the reservoir to recover crude oil through the production means, the improved process comprising injecting into the formation a micellar dispersion comprised of at least two different petroleum sulfonates, the sulfonates defined as:
 21. The process of claim 20 wherein the petroleum sulfonates have an aliphatic to aromatic proton ratio within the range of about 9.4 to about 14.5 moles/mole.
 22. The process of claim 20 wherein the distribution of the aliphatic to aromatic proton ratio of the two different sulfonates is of a magnitude of at least about 3.8 moles/mole. 